1. Field of the Invention
The present invention relates to an abrasive slurry and a preparation process of the abrasive slurry, which is suitable for the abrasion of thin film magnetic head for use in a hard disc drive (HDD), (particularly composite thin film magnetic head), a semiconductor integrated circuit, etc.
2. Description of the Related Art
With the enhancement of the recording capacity of HDD, the recent trend is more composite thin film magnetic heads performing magnetic induction writing by "write-inductive-element" and magnetic resistance reading by "read-MR-element" in combination (so-called MR head) to be used than magnetic induction thin film magnetic heads.
Under the circumstances, the surface roughness of the substrate on which MR elements are to be formed has been noted as a property governing the characteristics of magnetic resistance element (MR element) made of thin film laminate. JP-A-9-54914 (The term "JP-A" as used herein means an "unexamined Japanese patent publication (kokai)" ) proposes that the surface of alumina as underlayer of MR be slightly abraded.
Further, JP-A-8-96237 proposes that abrasion be conducted to eliminate undulation on the surface of upper shield due to the difference of thickness of substrate layer and the final step of abrasion involve the abrasion of Al.sub.2 O.sub.3 and NiFe.
These conventional art techniques disclose that abrasion can be used as a method for creating surface. However, it is necessary that the composite thin film magnetic head, e.g., alumina as insulating layer and NiFe constituting the magnetic circuit be abraded at the same time. There is no specific disclosure concerning an abrasive slurry which can be used to perform abrasion satisfying the requirements that the difference in the level between the two components be kept to not more than 1,000 .ANG. while keeping the surface roughness Max of not more than 100 .ANG. and Ra of not more than 10 .ANG..